1. TECHNICAL FIELD
The present invention relates to vibration welding structures for fixing an attachment to an instrument panel.
2. DESCRIPTION OF RELATED ART
Generally, in motor vehicles, an air conditioning duct is fixed to the back side of an instrument panel that is provided in front of a vehicle compartment, and cool or warm air is blown out from the air conditioning duct, through air blowoff apertures of the instrument panel, into the vehicle compartment.
As one method for attaching the air conditioning duct to the instrument panel, Japanese Patent Laid-Open Publication No. HEI-11-321287 for “Air Conditioning Duct and Method for Manufacturing and Installing the Air Conditioning Duct” discloses vibration welding one example of the disclosed vibration welding will be explained below with reference to the drawings.
FIGS. 16A to 16C are views explanatory of the conventional vibration welding structure for fixing an instrument panel attachment, and the following description will be made with the terms “instrument panel” and “air conditioning duct”, used in the laid-open publication, replaced with other terms “base member” and “attachment”, respectively.
As shown in FIG. 16A, a plurality of ribs 153 are formed on opposite end portions 151 and 152 of the base member 150, and the base member 150 is set in place with the ribs 153 oriented upward.
Then, the attachment 155 is positioned over the base member 150 and then lowered as depicted by arrows, so that opposite end portions 156 and 157 are placed on the ribs 153 of the base member 150.
Then, as shown in FIG. 16B, the attachment 155 is vibrated in a direction of arrows while a predetermined pressing force F is applied to the opposite end portions 156 and 157 of the attachment 155.
Due to the vibration of the attachment 155, friction heat is produced in contacts 158 between the ribs 153 of the base member 150 and the opposite end portions 156 and 157 of the attachment 155.
Then, as shown in FIG. 16C, the ribs 155 of the base member 150 and the opposite end portions 156 and 157 of the attachment 155 are vibration-welded together, so that the attachment 155 can be securely fixed to the base member 150.
Here, in order to vibration-weld the base member 150 and attachment 155, there is a need to freely vibrate the attachment 155 in an arrowed direction shown in FIG. 16A. Thus, if the attachment 155 is set on a predetermined position of the base member 150 with commonly-used positioning members, then vibration of the attachment 155 would be significantly restricted by the presence of the positioning members so that the attachment 155 can not be vibrated freely in the arrowed direction.
Because the attachment 155 to be vibration-welded to the base member 150 cannot be positioned properly with the commonly-employed positioning members as noted above, it is necessary for a human operator to set the attachment 155 on an appropriate position of the base member through a visual check or otherwise.
Consequently, the operations for setting the attachment 155 on the predetermined position of the base member tend to be time-consuming and impose a heavy load on the human operator, thereby undesirably preventing improved productivity.
It is therefore an object of the present invention to provide a vibration welding structure for fixing an instrument panel attachment which allows the attachment to be readily set on a predetermined position of the instrument panel without imposing a heavy load on a human operator.